refactoring in particle/formfactor context

• disambiguate fct names: detectorPosition(), particlePosition()
• mv Prism to ff

added Core label

changed title from disambiguate fct names: detectorPosition(), particlePosition() to refactoring in particle/formfactor context

changed the description

added 11 commits

• 2f03b761...52bb1e28 - 6 commits from branch develop
• 6d0b750e - disambiguate fct name: RectangularDetector::setDetectorPosition, detectorPosition
• 72b20cb8 - disambiguate fct name: IParticle::setParticlePosition, particlePosition
• f59f7390 - clang-format
• 7b8c4c57 - mv Prism to ff
• 4b179a52 - Prism -> namespace ff

Compare with previous version

merged

mentioned in commit 765af0a5